If you cannot find the Cr-5400 + Sds for a cheaper price than the 32gb and you want that, then get it.

For micros write speeds vary with the class. Read speeds should all be about the same.
The Psp would recognize 64gbs during M33-6 (Not sure when it first started to see that much) so it'll see it in 5.03 Gen-C or 5.03 Mhu.